Turbine airfoils, e.g., steam turbine diaphragm airfoils, can be subject to harsh environmental conditions during operation of a turbine, including exposure to high-temperature, high-pressure and high-moisture content steam. These operating conditions, among others, can cause damage to the turbine airfoils (e.g., at the trailing edge or tip), such that the airfoils require repair.
Conventional approaches for repairing turbine diaphragm airfoils (or, turbine static nozzles) generally fall into two categories: a) an all-weld build-up followed by manual grinding to restore a desired profile; and b) a partial partition repair (PPR), where a precision machined airfoil section is welded to replace the entire trailing edge of the airfoil, and some hand machining is performed on the weld to fit the precision machined airfoil section with the remaining original section of the airfoil. These processes are performed while the turbine diaphragm airfoils are in place in the diaphragm. In these cases, the repair can be ineffective (e.g., in failing to restore the desired flow path), costly, or both.